Wow, this is a hard question to answer.
I mostly agree with Shiraz, although I haven't been that much into cross dressing, or for as long. I'd be into it more if my wife hadn't reacted so strongly against it. But I've always loved boobs. There were several times when my wife and I were having sex, and she'd be sitting on top of me. I'd be reaching up and massaging her breasts, and say, "I love your boobies. I wish I had a pair of my own." And she'd always have some negative reaction.
But, like Shiraz, I really wish that I could feel what it's like to have the weight of them bouncing and swaying from my chest. Several years ago, my wife was out of town, and I borrowed one of her sports bras, stuffed it with water balloons, and went out for a short jog to try to imagine how women with big boobs feel jogging. But in the space of about a quarter mile, the strap was chafing a sore on my shoulder. When I was crossdressing, I had a pair of 36DD breast forms, and I tried to glue them to my chest and go out for a jog without a bra. But they were too heavy for the glue, and worked loose within a couple blocks.
I've thought about doing hormones, but I really couldn't see myself going to that expense. I even googled some articles on DIY HRT. I mentioned in another thread coming across an article on Quora about a guy who, in answer to the question, "Do men wear bras", explained that he had to wear one because some medications that he was taking caused him to sprout 38DDD's. And I was jealous.
And then I discovered this site. And, oh wow! It really is possible! But I have to be careful, because, psychologically, I have a tendency to grab hold of an idea like this and go off the deep end. It depends on my mood, but often I think, "If I grow boobs, I'm stuck with them for life. It's not like I can throw out the breast forms, bras, panties, and women's clothes like when I go through a purge, and have everything back the way it was. Do I really want to present myself like that for the rest of my life? What opportunities does that close off to me?"